1. Field of the Invention
The invention relates to a load detecting device for a roller bearing that is used to support, for example, a main shaft of a wind power generator, and a roller bearing apparatus.
2. Description of the Related Art
Wind, power generation becomes a focus of attention anew in recent years as an eco-friendly way to generate electric power without emitting carbon dioxide. Wind power generation has been rapidly becoming widespread in the world, while upsizing of a wind power generator has been proceeding in order to obtain a larger amount of generated power. In addition, in order to suppress an increase in the weight of a generator resulting from such upsizing, various structure improvements, such as employment of a thin-walled generator frame and a thin-walled journal box, for weight reduction have also been carried out. On the other hand, a load applied to a bearing that supports a main shaft of a rotor has been increasing due to the upsizing of the generator, and, in addition, a distribution of load applied to a bearing, particularly, rolling elements, has become complex due to improvement in the structure of the journal box, or the like. Therefore, it is especially important to accurately analyze the durability and service life of the bearing. Accordingly, there is a need for a measuring method by which a load applied to the rolling elements of the bearing is more accurately obtained.
In an existing art, in order to measure a load applied to a bearing, a strain gauge is provided inside a rolling element of the bearing as described in Japanese Patent Application Publication No. 7-77218 (W-A-7-77218). Specifically, in the technique described in JP-A-7-77218, a hole is formed along the axis of a roller, a strain gauge is provided on an inner surface of the hole, and the strain gauge is connected to a transmitting coil provided integrally with the roller. In addition, an annular receiving coil is provided on a side surface of an outer ring, and an output signal from the strain gauge, transmitted from the transmitting coil in real time, is received by the receiving coil. Then, the receiving coil is connected to an external computer, and received data are processed by the computer.